1. Field of the Invention
This invention relates to a torque transmitting device having a crankshaft connected to an internal combustion engine, and a gear connected with the rotating shaft to transmit a torque from the rotating shaft.
2. Background Art
A torque transmitting device having a rotating shaft and a gear connected with the rotating shaft to transmit a torque from the rotating shaft is known, as shown in Japanese Examined Patent Publication No. Hei 2-32445.
The prior art torque transmitting device mentioned above is provided with a crankshaft for an internal combustion engine, a camshaft-driving timing gear and a primary drive gear which are connected with the crankshaft to transmit a torque from the crankshaft, and which function as gears for transmitting the torque from the crankshaft to a camshaft and a clutch.
In the torque transmitting device, the cam-driving timing gear and primary drive gear are connected with the crankshaft by inserting a key into a keyway formed in the outer periphery of the crankshaft and in the inner periphery of these two gears.
In such a gear connection using the key as stated above, each of the gears needs centering with respect to the crankshaft, at both the outer periphery of the crankshaft and the inner periphery of each gear except the keyway. This prevents gear runout resulting from misalignment of the axis of the gears with the axis of the crankshaft. However, a member for transmitting the torque from the crankshaft to each gear is mounted by a single key, and the torque transmitting surface of the key is likely to be worn. In the event of wear in this portion, it becomes difficult to transmit a specific amount of torque.
In view of the above-described problems inherent in conventional devices, it is an object of the present invention to provide a torque transmitting device which enables the centering of the gears connected to the rotating shaft, and is subject to decreased wear of the torque transmitting surface.
A further object is to facilitate a fitting operation and accurate centering.
Another object is to enable more accurate setting of the intake and exhaust valves of an internal combustion engine, and to enable transmission of a greater driving torque in the internal combustion engine.
The torque transmitting device according to this invention has a rotating shaft and a gear connected with the rotating shaft to transmit the torque from the rotating shaft. In this torque transmitting device, the splined portion and the inner circumferential surface portion for centering formed in the inner periphery of the gear are fitted on the splined portion and the outer circumferential surface portion for centering formed in the outer periphery of the rotating shaft.
According to the invention, the outer peripheral surface for centering of the rotating shaft and the inner circumferential surface portion for centering of the gears are mutually fitted to allow accurate centering of the gears with respect to the rotating shaft, thereby preventing gear runout on the rotating shaft. This minimizes noise resulting from the gear runout.
In addition, because the splined portion of the gear is mounted on the splined portion of the rotating shaft to thereby transmit the torque from the rotating shaft to the gear through a plurality of splines, it is possible to reduce wear of the torque transmitting surface. Consequently, it is possible to transmit a great torque and to transmit a desired amount of torque for a prolonged period of time.
The outer circumferential surface portion for centering and the inner circumferential surface portion for centering may be clearance-fit, which enables easy mounting of a gear on the rotating shaft.
The outside diameter of the outer circumferential surface portion for centering may be larger than the outside diameter of the splined portion formed on the rotating shaft. Because of the larger outside diameter of the outer circumferential surface portion, the outer circumferential surface portion for centering and the inner circumferential surface portion for centering can be fitted without being affected by the fitting of the splined portion, which enables accurate centering. The rotating shaft is a crankshaft of the internal combustion engine and the gear is a cam-driving timing gear of the internal combustion engine, and therefore the crankshaft of the internal combustion engine and the cam-driving timing gear are accurately centered. It is thus possible to accurately set the valve timing of the intake and exhaust valves driven by the rotation of the camshaft.
The rotating shaft may be the crankshaft of the internal combustion engine, and the gear may be a primary drive gear of the internal combustion engine. Because the torque transmission is effected between the crankshaft and the primary drive gear through the splined portion, a great deal of driving torque can be transmitted from the crankshaft to the clutch even in an internal combustion engine having a large displacement and a high-speed internal combustion engine.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.